When the AC rotating machine in the free-run state not driven by the power converting apparatus is restarted, a frequency, a phase, and an amplitude of an output voltage supplied from the power converting apparatus need to be caused to coincide with a rotation frequency, a residual voltage phase, and an amplitude of the AC rotating machine in the free-run state. If the voltage phases and the amplitudes are different, a large current flows to the power converting apparatus. If the frequencies are different, sudden torque is caused in the AC rotating machine.
As means for solving such a problem, in a related art described in Patent Literature 1, a magnetic-flux-estimation-value correcting unit that corrects a boost of a magnetic flux estimation value in a process from coasting to restart of an electric motor vehicle is provided between an induction-machine-motor model unit that calculates a magnetic flux estimation value and a motor-current estimating unit that receives input of the magnetic flux estimation value from the induction-machine-motor model unit and calculates a current estimation value. Consequently, instability in restarting the AC rotating machine that is in the free-run state is reduced.